The proposed research involves regulatory and structure studies on glucose 6-phosphate dehydrogenase (G6PD) from Leuconostoc mesenteroides and developing rabbit erythrocytes. The bacterial enzyme utilizes either NAD ion or NADP ion as coenzyme. We have recently developed a dual wavelength assay, enabling us to monitor both reactions simultaneously using thionicotinmide analogs. We will use this technique to examine the effects of various potential regulatory compounds, such as NADPH, ATP, acetyl-CoA, on the differential activities of the NAD- and NADP-linked activities. We also plan to initiate sequencing studies, provided that we can grow suitable crystals for X-ray structural studies to be conducted in another laboratory simultaneously. We will isolate G6PD from mature erythrocyted, polychromatic erythroblasts and orthochromatic erythroblasts. Between the polychromatic and orthochromatic stage there is a large change in catalytic activity of G6PD. We wish to ascertain the cause of this change by performing detailed kinetic and structural studies on G6PD from erythrocytes and erythroblasts from the two developmental stages.